Find replace bash executable PHP script

gistfile1.php

#!/usr/bin/php
<?php
/**
  * Find replace tool 
  * Place it in the executable folder "/usr/local/sbin/"
  * Also, add an alias in the ~/.bashrc
  * Option should be -e for execute
  * Otherwise view the files only that contain the search term
  * Author: Antonis Flangofas
  * Date: 01/06/2014
  */
  
if ($argc < 5) {
	die("Not enough arguments\n");
}

$cmd = '';
$flag = $argv[1];
$find = addslashes($argv[2]);
$replace = addslashes($argv[3]);
$dir = $argv[4];

if (!file_exists($dir)) {
	die("Wrong directory\n");
}

if ($flag === '-e') {
	$cmd = "grep -rl $find $dir | xargs sed -i 's/$find/$replace/'";
} else {	
	$cmd = "grep -rl $find $dir";
}
exec($cmd, $output, $return_var);

if ($return_var != 0) {
	die("Error with your command $cmd\n");
}

if (!empty($output)) {
	array_walk($output, function($line) { echo "$line \n";  });	
}